Remove the door - reduces the weight significantly.

Wrap a tow strap around the center about knee high - Tie another strap to this one, pass it under the base, and tie to first strap on other side (like a big safe thong). You can then have up to 8 guys (two on each side) grab hold of the center strap and easily carry/lift it wherever you want. I've seen two large men move a 1000 lb safe using this method.

Also, as generalmeow alluded to, you can use lengths of 3/4" schedule 40 PVC to roll it across a floor. Used to do this in my basement over a tile floor - works like a charm.

Or, you could hire someone with an electric stair-climbing appliance dolly to do it for you. Call around to the local safe sellers - they do moving also.